King tides a glimpse of our coastal future?

Those who want a sneak peek of the future only need to head to the coast, where extreme tides have water levels rising to heights that researchers say will become the norm in a few decades.

The larger-than-normal tidal swings, known as king tides, will be creating dramatically high and low tide levels along the coast through Friday, according to the Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve. The California King Tides Initiative is inviting the public to take pictures of the coast during king tides and post them online to their Flickr photo-sharing website.

"The idea is to get citizens to go out and document high sea levels in areas that they care about and see what they look like under extreme conditions," said Kerstin Wasson, a research coordinator at the Elkhorn Slough Foundation.

The water level will change nearly 8 feet between low and high tide on Wednesday at Elkhorn Slough, the foundation estimated. A week ago, that change was just under 5 feet.

King tides are caused by the gravitational tugging of the moon and the sun. With the sun and full moon aligned as they are now, their gravitational pulls add up, increasing the force of the ocean.

"Picture the tide as a bulge being pulled out of the ocean," Wasson said.

The Elkhorn Slough Foundation recommended four sites for people to snap pictures of the tide levels: the Hudson Landing pullout along Elkhorn Road, Kirby Park in Watsonville, Moss Landing Beach and the Elkhorn Slough Reserve. But given the tides' astronomical origin, they can be seen all along the coast.

These are the second king tides of the year, with the first lasting from New Year's Day until Jan. 3.

Rising sea levels caused by climate change will eventually push shorelines to the high tide marks seen during the king tides and keep them there, Wasson said. In Monterey, the sea level is creeping up by an eighth of an inch per year or less, according to NOAA.

But the subtle changes will certainly add up, reshaping California's coastline and threatening low-lying natural ecosystems, such as the Elkhorn Slough's salt marsh, said Wasson. Salt marshes serve as natural filtration systems for runoff water heading for the ocean.

"We don't have many salt marshes to begin with," she said. "I want to see some remain for future generations."

But it will only be a matter of decades before the sea level rises enough to potentially wash out the marshes, Wasson said.

"I can't tell you if it will be three decades or five decades," she said. "But it's coming."